1. Field of the Invention
The present invention generally relates to a method and system for tuning micro-electro mechanical (MEMS) cantilevers or bars to change their resonant frequency, and more particularly to a method and system for tuning cantilevers or bars which are part of a filter mechanism used in telephony and the like.
2. Description of the Related Art
In a variety of electrical applications, such as telephony for example, certain incoming frequencies must be filtered, allowing only certain pre-set or desired frequencies to pass into the main circuit. To accomplish this selective passage, a tuned filter circuit is typically used.
In telephony (and other applications), extremely small filter circuits are used, some made by micro-electro mechanical means and devices. The filters contain mechanically resonant elements that vibrate when excited by their respective resonance frequency. When the applied frequency is off-resonance, there will be very little, if any, enhancement of the signal. Numerous papers and experiments describe the use of small cantilevers including the use of piezo-electric elements that have a distinct resonant frequency with a very high xe2x80x9cQxe2x80x9d (e.g., quality factor). Hence, such circuits function as very good filters due to the selectivity imposed by their geometry.
However, a problem arises in that, hitherto the present invention, there have been no known methods for tuning the frequency of the mechanical resonators. While means for trimming the resonators exist, these trimming means and methods do not allow the circuit to be tuned over time due to temperature or other environmental conditions.
Other problems of the conventional systems and methods include that the trimming is a one-time event and cannot be undertaken once the device leaves the production facility.
In view of the foregoing problems, drawbacks, and disadvantages of the conventional systems and methods, an object of the present invention is to provide a structure and method for tuning the frequency of mechanical resonators.
Another object of the present invention is to provide a method and system for tuning the resonator circuitry over time to compensate for temperature and other environmental conditions, slight mechanical jarring, changes in atmospheric pressure, and the like.
In a first aspect of the invention, a system (and method) is provided for tuning a resonant structure, which includes a predetermined material coating provided on the resonant structure; and a circuit for providing a variable magnetic field (e.g., preferably a variable dc magnetic field) adjacent the resonant structure, with the length of the resonant structure changing with the application of the variable field, thereby to selectively tune the resonant structure.
With the unique and unobvious features of the present invention, a method and system are provided for tuning the frequency of mechanical resonators, including when the mechanical resonators or a circuit incorporating the mechanical resonators, undergo temperature or other environmental changes.
Further, without tunability as provided by the invention, the filter circuit becomes useless should there be any small mechanical or environmental changes such as those listed above.